This present invention relates to a frame switcher and a switching, for example, the frame switcher and the switching method of recording and reproducing image signals with high efficiency while frames of images from a plurality of cameras of a monitoring system are switched, and a digital camera and the monitoring system using the frame switcher.
In recent years, a monitoring system has been widely used in which moving pictures or still pictures are picked up by digital cameras, the data from the cameras are processed and recorded by a recording/reproducing apparatus, and the data are processed, stored and reproduced by a reproducing apparatus. There is a conventional monitoring system in which the image signals from a plurality of digital cameras are transmitted to a recording/reproducing apparatus as, for example, shown in FIGS. 8 and 9.
The monitoring system shown in FIG. 8 uses a plurality of analog cameras A, B, C, D. The image signals from these cameras A-D are received by a monitoring system 1, sequentially switched at certain intervals of time by a switch 2 provided within the monitoring system 1, and stored in storage unit 3.
FIG. 9 shows outputs from the cameras A-D and an output to the storage unit 3 from the monitoring system 1. Each of the cameras A-D that is an analog camera always produces an image signal of frame units at certain intervals of time (for example, 1/30 second). Therefore, when the switch 2 switches the cameras A-D in turn at these time intervals, the frames are sent from all the different cameras to the storage unit as shown in FIG. 9.
However, when digital cameras for producing MPEG outputs are used in place of those cameras in order to record the image signals from the cameras, the frames from the cameras cannot be freely switched because the MPEG includes frames of P-frame and B-frame that depend on other frames.
Accordingly, it is an object of this invention to provide a frame switcher and a switching method for switching frames in MPEG in a digital monitoring system, and a digital camera and a monitoring system using the switcher.
It is another object of the invention to provide a frame switcher and a switching method for recording and reproducing image signals with high efficiency while frames of images from a plurality of cameras are switched, and a digital camera and a monitoring system using the switcher.
In order to achieve the above objects, the invention proposes a digital monitoring system constructed by connecting a plurality of MPEG cameras that can be synchronized, to a switcher for switching the image signals from the cameras, and a method of switching the image signals in which the MPEG cameras can be controlled to set the transmission timings and cycle times of I frames, and the image signals of one cycle from the cameras can be buffered, and only the necessary I frames can be extracted from the buffered image signals.
As a modification of the above embodiment, the transmission timings of I frames from the cameras are shifted in the method of switching the image signals in which the image signals of one cycle from the cameras are buffered and then only the necessary I frames are extracted.
In place of the buffering operation in the above two examples, the I frames from the cameras are transmitted with the transmission timings of I frames being shifted, and the switcher switches the image signals from the cameras in accordance with the transmission timings of I frames. In this case, while the transmission timings of I frames from the cameras are shifted, only the I frames from the cameras can be transmitted and received on a single channel in a time sharing manner.
Also, according to the invention, there is provided a digital camera having imaging means for picking up images, digitizing means for converting the produced image signal into a digital signal, timing control means for controlling the transmission timing of I frame of the image signal, setting means for setting the timing of the timing control means and the transmission cycle of I frame, and transmitting means for transmitting the image signal. In this camera, I frame extracting means for extracting the necessary I frame from the image signal can be further provided to extract and transmit the I frame of the image signal with a certain timing.
According to the invention, there is also provided a frame switcher having receiving means for receiving image signals from a plurality of cameras that produce digital image signals and are synchronized, buffer means for temporarily storing the image signals of one cycle received from the plurality of cameras, I frame extractor means for extracting only the I frames from the image signals stored in the buffer means, timing control means for controlling the operation timing of the I frame extractor means, setting means for setting the timing of the timing control means, and transmitting means for transmitting the image signals, whereby the I frames of image signals are extracted from the buffer means and transmitted with a certain timing. In the frame switcher, setting means is further provided to set the synchronization of the plurality of cameras so that the I frames are simultaneously transmitted and to set the cycle times so that they are transmitted with the same cycle time.
According to the invention, there is also provided another frame switcher having receiving means for receiving image signals from a plurality of cameras that produce digital image signals and are synchronized, channel switching means for switching channels on which the image signals are received, to a channel for a camera that is transmitting an I frame, timing control means for controlling the switching timing of the channel switching means, setting means for setting the timing of the timing control means, and transmitting means for transmitting the image signals, whereby the I frames of image signals are received and transmitted with a certain timing. In the frame switcher, buffer means are provided for storing part of I frame data of the image signals received from the plurality of cameras. In addition, setting means is provided to set the synchronization of the plurality of digital cameras so that the transmission timings of I frames are made different and set so that the transmission cycle times of I frames are same.
With those constructions, even though digital cameras are used, the images picked up by a plurality of cameras are efficiently switched for their frames, and transferred to the recorder or reproducer.
A digital monitoring system of claim 1 is constructed by MPEG cameras that are synchronized, and a switcher. The cameras are set as to the transmission timings and transmission cycle times of I frames. The image signals of one cycle from the cameras are buffered, and only the necessary I frames are extracted from the buffered image signals. Even though the digital image signals include frames depending upon other frames, such as P frame and B frame, the frames are switched so that the desired I frames are received.
A digital monitoring system of claim 2 is constructed by MPEG cameras that are synchronized, and a switcher. The cameras are set as to the transmission timings and transmission cycle times of I frames. The image signals of one cycle from the cameras are buffered, and only the necessary I frames are extracted from the buffered image signals. In the extraction process, the transmission timings of I frames from the plurality of cameras are shifted, and the digital image signals are received by frame switching.
A digital monitoring system of claim 3 is constructed by MPEG cameras that are synchronized, and a switcher. The cameras are set as to the transmission timings and transmission cycle times of I frames. The switcher switches the image signals from the cameras in accordance with the transmission timings of I frames. The transmission timings of I frames from the plurality of cameras are shifted so that the image signals are accurately and fast received with less buffer.
A digital monitoring system of claim 4 is constructed by MPEG cameras that are synchronized, and a switcher. The cameras are set as to the transmission timings and transmission cycle times of I frames. The switcher switches the image signals from the cameras in accordance with the transmission timings of I frames. The transmission timings of I frames from the plurality of cameras are shifted so that only the I frames are transmitted and that a single channel is shared by the plurality of cameras in a time sharing manner. Thus, the frequency band on the network between the cameras and the switcher is effectively used.
A method of switching image signals of claim 5 uses a plurality of cameras that produce digital image signals and are synchronized, and a switcher for switching the image signals from the plurality of cameras. The method has the steps of setting synchronization of a plurality of cameras so that the I frames are simultaneously transmitted, and the transmission cycle times of I frames so that the I frames are transmitted with the same cycle time, buffering the image signals of one cycle from the plurality of cameras, and extracting, by switching only the necessary I frames, from the buffered image signals. Thus, even though the digital image signals include frames depending upon other frames such as P frame and B frame, the digital image signals are received by frame switching.
A method of switching image signals of claim 6 uses a plurality of cameras that produce digital image signals and are synchronized, and a switcher for switching the image signals from the plurality of cameras. The method has the steps of setting synchronization of a plurality of cameras so that I frames are simultaneously transmitted, and the transmission cycle times of I frames so that the I frames are transmitted with the same cycle time, buffering the image signals of one cycle from the plurality of cameras, and extracting, by switching the necessary I frames, from the buffered image signals while the transmission timings of I frames from the cameras are shifted. Thus, the digital image signals are received by frame switching.
A method of switching image signals of claim 7 uses a plurality of cameras producing digital image signals and synchronized, and a switcher for switching the image signals from the plurality of cameras. The method has the steps of setting synchronization of a plurality of cameras so that the transmission timings of I frames are made different, and the transmission cycle times of I frames so that the I frames are transmitted with the same cycle time, and transmitting the I frames in such a manner that they are switched in synchronism with the above different transmission timings of I frames and that the operation timings of the cameras are shifted. Therefore, the image signals are fast and accurately received with less buffer.
A method of switching image signals of claim 8 uses a plurality of cameras producing digital image signals and synchronized, and a switcher for switching the image signals from the plurality of cameras. The method has the steps of setting synchronization of a plurality of cameras so that the transmission timings of I frames are made different, and the transmission cycle times of I frames so that the I frames are transmitted with the same cycle time, and transmitting only the I frames in such a manner that the I frames are switched in synchronism with the above different transmission timings of I frames and that the operation timings of the cameras are shifted, in which a single channel is shared by the plurality of cameras in a time sharing manner. Thus, the frequency band on the network between the cameras and the switcher are effectively used.
A digital camera of claim 9 has imager means for picking up images, digitizing means for converting the produced image signal into a digital signal, timing control means for controlling a transmission timing of I frame of the image signal, setting means for setting a timing of the timing control means and a transmission cycle time of I frame, and transmitting means for transmitting the image signal. Thus, the I frame of the image signal are transmitted with a certain timing and in a different way according to the settings in the system.
A digital camera of claim 10 has imager means for picking up images, digitizing means for converting the produced image signal into a digital signal, I frame extracting means for extracting the necessary I frame from the image signal, timing control means for controlling a transmission timing of the I frame, setting means for setting a timing of the timing control means and a transmission cycle time of I frame, and transmitting means for transmitting the image signal. Thus, since the I frame of the image signal are transmitted to the switcher with a certain timing, the construction of the switcher and the necessary processing load on the switcher are simplified and reduced, respectively. In addition, it is possible to decrease the amount of data to be transmitted as the image signal.
In a digital camera of claim 11 according to claim 9 or 10, the setting means is provided to set a synchronization of a plurality of cameras so that I frames from the cameras are simultaneously transmitted, and a transmission cycle times so that the I frames are transmitted with the same cycle time. Even though the digital image signals include frames depending upon other frame, such as P frame and B frame, the switcher receiving the image signals switches the frames to easily receive the I frames.
In a digital camera of claim 12 according to claim 9 or 10, the setting means is provided to set synchronization of a plurality of cameras so that transmission timings of I frames are made different, and transmission cycle times so that the I frames are transmitted with the same cycle time. Thus, the switcher receiving the digital image signals switches the image signals with less buffer and delay to receive the I frames.
A frame switcher of claim 13 has receiving means for receiving the image signals from a plurality of cameras that produce digital image signals and are synchronized, buffer means for temporarily storing the image signals of one cycle received from the plurality of cameras, I frame extracting means for extracting only the necessary I frames from the buffered image signals, timing control means for controlling an operation timing of the I frame extracting means, setting means for setting a timing of the timing control means, and transmitting means for transmitting the image signals. Since the I frames of the image signals are extracted from the buffer means and transmitted with a certain timing, the digital image signals are received by frame switching even though the digital image signals include frames depending upon other frames such as P frame and B frame.
In a frame switcher of claim 14 according to claim 13, the setting means is provided to set synchronization of a plurality of cameras so that I frames are simultaneously transmitted, and a transmission cycle times so that the I frames are transmitted with the same cycle time. Thus, even though the digital image signals include frames depending upon other frames such as P frame and B frame, the digital image signals are switched so that the I frames are easily received.
A frame switcher of claim 15 has receiving means for receiving the image signals from a plurality of cameras that produce digital image signals and are synchronized, channel switching means for switching the channels on which the image signals are received to a channel for the camera that is transmitting the I frame, timing control means for controlling the switching timing of the channel switching means, setting means for setting a timing of the timing control means, and transmitting means for transmitting the image signals. Thus, since the I frames of image signals are transmitted with a certain timing, they are fast and accurately received.
In a frame switcher of claim 16 according to claim 15, the buffer means is provided to store part of I frame data of the image signals received from a plurality of cameras. Thus, the I frames are received orderly even though the I frames from the cameras are received and overlapped when the channel switching means is switching.
In a frame switcher of claim 17 according to claim 13, 15 or 16, the setting means is provided to set synchronization of a plurality of cameras so that transmission timings of I frames are made different, and transmission cycle times so that the I frames are transmitted with the same cycle time. Thus, the image signals are fast and accurately received with less buffer.